A multiplexer or mux is a device that performs multiplexing; it selects one of many analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output. An electronic multiplexer makes it possible for several signals to share one device or resource, for example, one analog to digital converter or one communication line, instead of having one device per input signal. On the other end, a demultiplexer (or demux) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input. A multiplexer is often used with a complementary demultiplexer on the receiving end.
An electronic multiplexer may be considered as a multiple-input, single-output switch, and a demultiplexer as a single-input, multiple-output switch. The schematic symbol for a multiplexer is an isosceles trapezoid with the longer parallel side containing the input pins and the short parallel side containing the output pin.
FIG. 1 provides a schematic of multiplexer channel 100 as known in the prior art. Multiplexer channel includes input 110, pass transistor 120, p-channel selection transistor 140, n-channel selection transistor 150, selection line 160, and output 170. When select line 160 is pulled high, transistor 150 turns on and transistor 140 turns off. This pulls the gate of transistor 120 down to Vss, turning on transistor 120, which passes input 110 to output 170. There is a need for a high voltage tolerant multiplexing device without a reduction in accuracy.